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Thermoresponsive Hydrogels from Symmetrical Triblock Copolymers Poly(styrene-block-(methoxy diethylene glycol acrylate)-block-styrene)

  • A series of symmetrical, thermo-responsive triblock copolymers was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization, and studied in aqueous solution with respect to their ability to form hydrogels. Triblock copolymers were composed of two identical, permanently hydrophobic outer blocks, made of low molar mass polystyrene, and of a hydrophilic inner block of variable length, consisting of poly(methoxy diethylene glycol acrylate) PMDEGA. The polymers exhibited a LCST-type phase transition in the range of 20-40 degrees C, which markedly depended on molar mass and concentration. Accordingly, the triblock copolymers behaved as amphiphiles at low temperatures, but became water-insoluble at high temperatures. The temperature dependent self-assembly of the amphiphilic block copolymers in aqueous solution was studied by turbidimetry and rheology at concentrations up to 30 wt %, to elucidate the impact of the inner thermoresponsive block on the gel properties. Additionally, small-angle X-ray scattering (SAXS)A series of symmetrical, thermo-responsive triblock copolymers was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization, and studied in aqueous solution with respect to their ability to form hydrogels. Triblock copolymers were composed of two identical, permanently hydrophobic outer blocks, made of low molar mass polystyrene, and of a hydrophilic inner block of variable length, consisting of poly(methoxy diethylene glycol acrylate) PMDEGA. The polymers exhibited a LCST-type phase transition in the range of 20-40 degrees C, which markedly depended on molar mass and concentration. Accordingly, the triblock copolymers behaved as amphiphiles at low temperatures, but became water-insoluble at high temperatures. The temperature dependent self-assembly of the amphiphilic block copolymers in aqueous solution was studied by turbidimetry and rheology at concentrations up to 30 wt %, to elucidate the impact of the inner thermoresponsive block on the gel properties. Additionally, small-angle X-ray scattering (SAXS) was performed to access the structural changes in the gel with temperature. For all polymers a gel phase was obtained at low temperatures, which underwent a gel-sol transition at intermediate temperatures, well below the cloud point where phase separation occurred. With increasing length of the PMDEGA inner block, the gel-sol transition shifts to markedly lower concentrations, as well as to higher transition temperatures. For the longest PMDEGA block studied (DPn about 450), gels had already formed at 3.5 wt % at low temperatures. The gel-sol transition of the hydrogels and the LCST-type phase transition of the hydrophilic inner block were found to be independent of each other.show moreshow less

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Author details:Anna Miasnikova, André LaschewskyORCiDGND, Gabriele De Paoli, Christine M. PapadakisORCiDGND, Peter Müller-Buschbaum, Sergio S. Funari
DOI:https://doi.org/10.1021/la204665q
ISSN:0743-7463
Title of parent work (English):Langmuir
Publisher:American Chemical Society
Place of publishing:Washington
Publication type:Article
Language:English
Year of first publication:2012
Publication year:2012
Release date:2017/03/26
Volume:28
Issue:9
Number of pages:12
First page:4479
Last Page:4490
Funding institution:Deutsche Forschungsgemeinschaft DFG [SPP1259, LA611/7, PA771/4, MU1487/8]
Organizational units:Mathematisch-Naturwissenschaftliche Fakultät / Institut für Chemie
Peer review:Referiert
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